nutrients Review
Dietary Capsaicin Protects Cardiometabolic Organs from Dysfunction Fang Sun, Shiqiang Xiong and Zhiming Zhu * The Center for Hypertension and Metabolic Diseases, Department of Hypertension and Endocrinology, Daping Hospital, Third Military Medical University, Chongqing Institute of Hypertension, Chongqing 400042, China;
[email protected] (F.S.);
[email protected] (S.X.) * Correspondence:
[email protected]; Tel.: +86-23-68767849; Fax: +86-23-68705094 Received: 14 February 2016; Accepted: 15 March 2016; Published: 25 April 2016
Abstract: Chili peppers have a long history of use for flavoring, coloring, and preserving food, as well as for medical purposes. The increased use of chili peppers in food is very popular worldwide. Capsaicin is the major pungent bioactivator in chili peppers. The beneficial effects of capsaicin on cardiovascular function and metabolic regulation have been validated in experimental and population studies. The receptor for capsaicin is called the transient receptor potential vanilloid subtype 1 (TRPV1). TRPV1 is ubiquitously distributed in the brain, sensory nerves, dorsal root ganglia, bladder, gut, and blood vessels. Activation of TRPV1 leads to increased intracellular calcium signaling and, subsequently, various physiological effects. TRPV1 is well known for its prominent roles in inflammation, oxidation stress, and pain sensation. Recently, TRPV1 was found to play critical roles in cardiovascular function and metabolic homeostasis. Experimental studies demonstrated that activation of TRPV1 by capsaicin could ameliorate obesity, diabetes, and hypertension. Additionally, TRPV1 activation preserved the function of cardiometabolic organs. Furthermore, population studies also confirmed the beneficial effects of capsaicin on human health. The habitual consumption of spicy foods was inversely associated with both total and certain causes of specific mortality after adjustment for other known or potential risk factors. The enjoyment of spicy flavors in food was associated with a lower prevalence of obesity, type 2 diabetes, and cardiovascular diseases. These results suggest that capsaicin and TRPV1 may be potential targets for the management of cardiometabolic vascular diseases and their related target organs dysfunction. Keywords: chili pepper; capsaicin; TRPV1; metabolic syndrome; obesity; hypertension; diabetes
1. Introduction A lot of protective natural compounds had been found for their neuroprotective properties in preventing diseases and inflammation [1–4]. Chili peppers have become a vital part of culinary cultures worldwide and have a long history of use for flavoring, coloring, and preserving food, as well as for medical purposes. Although some people are intolerant to pungency because of the sensation of heat and pain in the oral cavity, as well as varying degrees of gastrointestinal side effects, there remain many loyal consumers of this original South American plant. The increased use of chili peppers in food is a major trend around the world [5]. Capsaicin, the pungent ingredient in chili peppers, is an indispensable condiment, and it has shifted from an industrialized purified product to a daily nutrient. The beneficial effects of capsaicin have been validated in experimental and population studies. The receptor for capsaicin is called the transient receptor potential vanilloid subtype 1 (TRPV1). TRPV1 belongs to the transient receptor potential (TRP) family, which is a heterogeneous group of non-selective cation channels. Based on their structural homology, mammalian TRP channels can be divided into six subfamilies, including the TRP canonical (TRPC; TRPC1–7), TRP vanilloid (TRPV; TRPV1–6), TRP melastatin (TRPM; TRPM1–8), TRP mucolipin (TRPML; TRPML1–3), TRP Nutrients 2016, 8, 174; doi:10.3390/nu8050174
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Nutrients 2016, 8, 174
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ankyrin (TRPA; TRPA1), and TRP polycystin (TRPP; TRPP2, TRPP3, TRPP5) subfamilies [6]. It is well documented that TRP channels are involved in visual, auditory, taste, and pain signal transduction pathways. Emerging evidence indicates that TRP channels also participate in the regulation of cell survival and growth, mineral absorption, body fluid balance, gut motility, and cardiovascular function [7]. TRPV1 is a highly investigated TRPV subfamily member. In addition to its classical role in the nervous system, TRPV1 plays important roles in the maintenance of physiological homeostasis. Capsaicin is passively absorbed with greater than 80% efficiency in the stomach and upper portion of the small intestine and is transported by albumin in the blood [8]; therefore, it may extensively activate local TRPV1 channels in different organs or tissues to initiate a series of physiological effects. 2. Physiological Function of TRPV1 TRPV1 is widely expressed in the brain, sensory nerves, dorsal root ganglia, bladder, gut, and blood vessels [9,10]. TRPV1 is a ligand-gated non-selective cation channel, which is activated by multiple stimuli, including heat (>43 ˝ C), voltage, low pH (43 ˝ C), acid (pH < 5.9), voltage, and various domains. It has a short, pore‐forming hydrophobic stretch between the fifth and sixth transmembrane lipids. Additionally, capsaicin activates TRPV1 and triggers cation influx and various subsequent domains. TRPV1 is activated by noxious heat (>43 °C), acid (pH
